The present invention relates to a vertical spindle duplex head for a grinder and its grinding method for grinding the end face of workpieces to be shaped into a spherical surface, while rotating and revolving the workpieces.
The vertical spindle duplex head grinder which has the receiving wheel and the pressure wheel driven by their individual driving device is well-known. In that case, since two driving devices are provided, two general-purpose motors are used as the driving sources thereof. Nevertheless, the difference in efficiency between these two general-purpose motors and the slipping and instability of the motors' rotation due to grinding resistance makes it extremely difficult to maintain accurately the ratio between their rotational speeds, resulting in the problem of facing a difficulty in establishing a constant grinding condition.